Background and Aims: Legionnaires’ disease is seen in sporadic and epidemic form. The most prevalent cause is Legionella pnuemophilia (L.pneumophila), which produces a severe disease in vulnerable individuals with a high fatality rate. This study was conducted due to the wide and universal distribution of the Legionnaires’ disease, lack of conventional and accessible diagnostic method, unresponsiveness to conventional antibiotic therapy in some pneumonia patients and the lack of any report about it in Kashan city, Iran.Materials and Methods: This descriptive study was performed on 117 pneumonia patients hospitalized in Kashan Shahid Beheshti hospital. After obtaining the consent form, urine specimens of the patients for isolating and detecting of L.pneumophila were examined using the enzyme-linked immunosorbent assay method. A questionnaire containing information about demographic, clinical and para-clinical findings was filled out by the researcher.Results: From a total of 117 cases, 11 (9.4%) urinary antigens of L.pnuemophilia were detected. 48 cases (41%) were males and 69 (59%) were females. The most cases were in ≥60 age group. There was no significant association between sex, age, job with number of L.pneumophila cases, but there was a significant correlation between smoking, disturbance of consciousness, increase of aspartate aminotransferase and the prevalence of Legionella.Conclusions: The prevalence of L.pnuemophilia among the pneumonia patients was 9.4%. Considering that there is a significant association between smoking and disturbance of consciousness, education about avoiding of smoking and considering L.pnuemophilia as a cause of pneumonia in patients with disturbance of consciousness is recommended.